Downward curling leaves

It does look like overwatering to me. Seedlings require little food and water, in veg you need a decent amount. In the 1st half of flowering they need a lot more to bulk up and then once they slow down bulking, you need to slow down watering and feeding. Your plants have done most of the bulking already and aren't creating much more biomass, so they won't need as much nutrients and water anymore. Think of how humans eat through their life (normal healthy ones at least :P). Babies eat very little. Small kids eat a bit more, but not too crazy normally. Teens are about to hit a growth spurt and can eat like crazy. In your 40s and 50s you need a moderate amount. Older people will have small meals and be fine. Your plant is the same, it is important to slow down watering and feeding as it slows bulking up to match the needs of the plant. Just because it's a big plant, doesn't mean you must keep watering at the same rate as you did early or mid flower.